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cocoon, having acquired half of Its proper 

 length, is rounded Into a cap and finally 

 is closed. The building-methods of the 

 Tachytes-larva remind me of a mason con- 

 structing a round chimney, a narrow tower 

 of which he occupies the centre. Turning 

 on his own axis and using the materials 

 placed to his hand, he encloses himself little 

 by Httle In his sheath of masonry. In the 

 same way the worker encloses Itself In Its 

 mosaic. To build the second half of the 

 cocoon, the larva turns round and builds In 

 the same way on the other edge of the orig- 

 inal ring. In about thirty-six hours the 

 solid shell Is completed. 



I am rather interested to see the Bembex 

 and the Tachytes, two workers in the same 

 guild, employ such different methods to 

 achieve the same result. The first begins 

 by weaving an eel-trap of pure silk and next 

 encrusts the grains of sand inside; the sec- 

 ond, a bolder architect, is economical of the 

 silk envelope, confines itself to a hanging 

 girdle and builds course by course. The 

 building-materials are the same: sand and 

 silk; the surroundings amid which the two 

 artisans work are the same: a cell in a soil 

 of sandy gravel; yet each of the builders 

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